Methylchloroform (i.e., 1,1,1-trichloroethane) and trichloroethylene are industrial solvents widely used for degreasing. Their usefulness in degreasing metals, especially light metals such as aluminum, is restricted because of their high degree of sensitivity to decomposition in the presence of aluminum. This sensitivity is particularly acute when methylchloroform and/or trichloroethylene contacts aluminum containing freshly exposed surfaces such as when the aluminum is scratched while submerged in the chlorinated hydrocarbon. Without the protection offered by formulating with the appropriate additive under such circumstances, methylchloroform and trichloroethylene decompose to various undesirable reaction products. Methylchloroform in particular decomposes into an unmanageable black tarry mass in a relatively brief period. It is thus commonplace to add to solvent compositions containing methylchloroform and/or trichloroethylene certain additives to protect against decomposition of these materials, including that type of decomposition which is particularly acute in the presence of freshly exposed surfaces of aluminum.
Even though stabilized with appropriate additives, methylchloroform and trichloroethylene do decompose, albeit at a much reduced rate as compared to solvent compositions not containing the additives. Unfortunately, whether stabilized with such additives or not, the decomposition products of methylchloroform and trichloroethylene include acid species which are corrosive to many of the metals being degreased. An acid species which is particularly troublesome is hydrogen chloride. It has accordingly been the usual practice to add an acid acceptor to methylchloroform and/or trichloroethylene to remove acidic species from the system. Epoxy compounds such as the 1,2 and 2,3 isomers of butylene oxide have been used for this purpose. Not only must the acid acceptor be compatible with other materials in the solvent system and perform its acid accepting function, but the products of the acid accepting reaction must be stable, compatible and essentially non-corrosive toward metals being degreased. These constraints impose considerable limitations on the types of acid acceptors which may be used in these chlorinated hydrocarbon systems.